Purification of 1-dehydro-17alpha-methyltestosterone contaminated by selenium



hire States atent 3,048,503 Patented Aug. 7, 1%62 ire 3,048,603PURIFICATION OF I-DEHYDRO-l'Toc-IWETHYL- TESTGSTERONE CUNTAIVHNATED BYSE- lLENlUM i Alfred Hunger, Basel, Switzerland, and John BenjaminZiegler, Summit, N.l., assignors to Ciba Corporation, a corporation ofDelaware No Drawing. Filed Dec. 3, 1959, er. No. 856,901

8 Claims. (Cl. 260-3974) The introduction of a 1,2-double bond into a A-3-oxosteroid by dehydrogenating the latter with selenium oxide (orselenious acid, of which selenium oxide is the anhydride) represents avery convenient one-step procedure for the preparation of thephysiologically important A 3-oxo-steroids. This method is moreeconomical than the conventional halogenation and dehydrohalogenation orthe microbiological dehydrogenation, which procedures generally involvemore steps and/ or the formation of undesired by-products.

It has been found that l7a-methyl-testosterone can be converted in highyield to l-dehydro-17a-methyl-testosterone, a highly active anabolicagent known under the generic name methandrostenolone, by treating theformer with selenium oxide (or selenious acid) in the presence of asolvent or solvent mixture, such as, for example, a tertiary loweralkanol, e.g. tertiary amyl alcohol and the like, a lower alkanecarboxylic acid, e.g. acetic acid and the like, or any other suitablesolvent. Despite all the advantages of the dehydrogenation method of17amethyl-testosterone with selenium oxide (or selenious acid), theresidual amounts of selenium, particularly of organically boundselenium, contaminating the resulting crude l-dehydro-l7wmethyltestosterone, represent a serious drawback of this dehydrogenationmethod. In view of its use as a therapeutical agent, the final producthas to :be virtually free from impurities, such as organically boundselenium, in order to comply with the required degree of purity.Although a major part of the selenium impurities in the crude productmay be removed, for example, by filtration, adsorption and elution,recrystallization methods and the like, a certain amount of theseundesired by-products still remain as contaminants and cannot beeliminated by the above-mentioned conventional methods. This amount isinvariably in excess of "the quantity of selenium tolerated inpharmaceutical compositions by health authorities.

We have now found a simple and economical process for the removal ofselenium impurities contaminating 1- dehydro-l7a-methyl-testosteroneobtained by dehydrogenating 17a-methyl-testosterone with selenium oxideor selenious acid, which comprises treating the crude 1-dehydro-l7a-methyl-testosterone with hydrogen peroxide, separating theresulting acidic fraction from the neutral fraction, treating theneutral fraction with an adsorbent, and recovering the purifiedl-dehydro-17e-methyl-testosterone.

This procedure yields the desired l-dehydro-17umethyl-testosteronevirtually free from contaminating selenium impurities. Surprisingly, thedouble bonds in the A-ring and/ or the substituents attached to the17-position of the l-dehydro-l7u-methyl-testosterone are not aifected bythe treatment with hydrogen peroxide, which is a strong oxidizingreagent; no degradation products are observed and the yields of purematerial are excellent.

The crude l-dehydro-l7e-methyl-testosterone, which is obtained from thedehydrogenation of 17u-methyl-testosterone and is used as the startingmaterial in the process of this invention, contains from about 1,000 toabout 15,000 parts per million of organically bound selenium. Although aportion of this impurity may be removed by conventional methods, such asfiltration of a solution of the crude product, adsorption on anadsorbent and subsequent elution, recrystallization and the like, suchpurification steps are not necessary prior to the processof theinvention, and the crude material obtained from the dehydrogenation:procedure can be used directly in the first step of the procedure ofthis invention.

Treatment with hydrogen peroxide (used, for example, inthe form of anaqueous solution of about 30 percent strength) is preferably carried outat room temperature and in the presence of a solvent, suchas, forexample, an organic carboxylic acid, particularly a lower alkanecarboxylic acid, e.g. acetic acid and the like, or any other suitableorganic solvent, which does not participate in the reaction or isaliected by hydrogen peroxide.

The acidic fractions in the resulting reaction product are removed, forexample, by extracting a solution of the product in an organic-solventmay be used directly in the next step.

The neutral fraction, preferably kept in solution with one of thesolvents used in the previous step, such as, for example, toluene, ethylacetate or any other suitable solvent, is then treated with anadsorbent. This treatment may be carried out, for example, by passingthe solution through a column containing the adsorbent, or by adding theadsorbent to the solution and subsequently filtering oh? the solidmaterial. Aluminum oxide (neutral or basically activated), silicagel,diatomaceous earth or any equivalent material may serve as an adsorbent.If necessary, the desired 1-dehydro-l7a-methyl-testosterone iscompletely liberated from the adsorbent by washing the latter with anadditional amount of solvent.

The purified 1-dehydro-17a-methyl-testosterone is then recoveredaccording to known procedures, for example, by evaporating the solutionafter the treatment with the adsorbent and recrystallizing the residuefrom an appropriate solvent, for example, from ethyl acetate and thelike.

With the purification procedure of the present invention, the content oforganically bound selenium can be kept considerably below twenty fiveparts per million, for example, at from about five to about fifteenparts per million, which amounts are sutiicient to satisfy therequirements of health authorities.

The following example illustrates the invention; temperatures are givenin degrees centigrade.

Example 6.5 g. of l-dehydro-17ot-methyl-testosterone, which containsabout 8,000 parts per million of organically bound selenium, isdissolved in 13 ml. of glacial acetic acid; 0.65 g. of 30 percentaqueous hydrogen peroxide is added and the reaction mixture is allowedto stand at room temperature for twenty hours. The reaction mixture isthen diluted with 52 ml. of water, the precipitate is filtered oil andthoroughly washed with water.

2.0 g. of the resulting product is dissolved in 20 ml. of toluene, andthe organic solution is washed three times with 20 percent aqueoussodium carbonate to remove the acidic parts in the organic solution; thelatter is dried over magnesium sulfate and passed through a columncontaining 6.0 g. of aluminum oxide (basic, to 200 a mesh). The columnis washed with 200 ml. of toluene, the organic solvent is evaporated andthe residue is crystallized from ethyl acetate to yield the purifiedl-dehydro- 17u-rnethyl-testosterone, MP. 166168, containing 13 parts permillion of selenium impurities.

The starting materialmay be prepared as follows: A solution of 50 g. of17a-methyl-testosterone in 1,000 ml. of tertiary amyl alcohol and 25 ml.of acetic acid is treated with 18.4 g. of selenium oxide, by adding thelatter in portions to the refluxing solution over a period of eighthours. Refluxing is continued for sixteen hours; the reaction mixture isthen filtered and ethyl acetate is added to the filtrate. The organicsolution is washed with a saturated aqueous sodium chloride solution andwith a saturated sodium carbonate solution, dried over magnesium sulfateand evaporated under reduced pressure. The residue is-crystallized fromethyl acetate to yield crude l-dehydro-17x-methyl-testosteronecontaining about 8,000 parts per million of organically bound selenium.

What is claimed is:

1. Process for the removal of selenium impurities contaminating1-dehydro-17u-methyl-testosterone obtained by dehydrating'17a-methyl-testosterone with a member of the group consisting ofselenium oxide and selenious acid, which comprises treating a solutionof the crude l-clehydro-l7u-methyl-testosterone in a lower alkanecarboxylic acid with hydrogen peroxide, separating the resulting acidicfraction from the neutral fraction, treating said neutral fraction withan adsorbent, and recovering 4 the purified1-dehydro-17a-methyl-testosterone from the neutral fraction,

2. Process according to claim 1, wherein a solution of the crude1-del1ydro-17a-methyl-testosterone in acetic acid is used.

3. Process according to claim 1, wherein an aqueous solution of hydrogenperoxide of about 30 percent strength is used.

4. Process according to claim 1, wherein the treatment with hydrogenperoxide is carried out at room temperature.

5. Process according to claim 1, wherein the resulting acidic fractionis separated from the neutral fraction by 7. Process according to claim1, wherein a solution of V the neutral fraction is treated with aluminumoxide as an adsorbent.

8. Process according to claim 1, wherein the purified1-dehydro-17ot-methyl-testosterone is recovered from the neutralfraction by recrystallization.

References Cited in the file of this patent Florey et al.: J.O.C., 212,406-409 (1957). Baran: J. Am. Chem. Soc., 80, 1687-1691 (1958).

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3.048603 Auguet 1962 Alfred Hunger et a1 It is hereby certified that errorappears in the above numbered patent requiring correction and that thesaid Letters Patent should read as corrected below.

7 Column l line 25 for "recrystallization" read crystallization Signedand sealed this 5th day of May 1964.

(SEAL) Attest:

ERNEST W, SWIDER Attesting Officer EDWARD J. BRENNER Commissioner ofPatents

1. PROCESS FOR THE REMOVAL OF SELENIUM IMPURTIES CONTAMINATING1-DEHYDRO-17A-METHYL-TESTOSTERONE OBTAINED BY DEHYDRATING17A-MATHYL-TESTOSTERONE WITH A MEMBER OF THE GROUP CONSISTING OFSELENIUM OXIDE AND SELENIOUS ACID, WHICH COMPRISES TREATING A SOLUTIONOF THE CRUDE 1-DEHYDORO-17A-METHYL-TESTOSTERONE IN A LOWER ALKANECARBOXYLIC ACID WITH HYDROGEN PEROXIDE, SEPARATING THE RESULTING ACIDICFRACTION FROM THE NEUTRAL FRACTION, TREATING SAID NEUTRA FACTION WITH ANABSORBENT, AND RECOVERING THE PURIFIED 1-DEHYDRO-17A-METHYL-TESTOSTERONEFROM THE NEUTRAL FRACTION.